Fix some doxygen warnings.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56294 75b3775d-3801-0410-9e12-e2e43121521d
Fix a doxygen warning.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56295 75b3775d-3801-0410-9e12-e2e43121521d
Fix a doxygen warning.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56296 75b3775d-3801-0410-9e12-e2e43121521d
Fix some doxygen warnings.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56297 75b3775d-3801-0410-9e12-e2e43121521d